Thiolcarbamate sulfoxide herbicides that are the subject of the present invention have been disclosed in U.S. Pat. No. 3,897,492, 3,928,436, 3,598,859, 3,989,684 and various foreign patents.
These compounds exhibit excellent herbicidal activity against a variety of undesirable grasses and broadleaf plants. However, it has been discovered that their herbicidal activity is reduced when they are utilized in dry soil.
In other words, when the sulfoxide herbicide is applied to dry soil or applied to soil that becomes dry after application, deactivation of the herbicide occurs with resulting reduction of herbicidal activity. Generally such deactivation is most troublesome in those soils that contain relatively low amounts of clay, for example, sandy loam soil and those soils that are low in organic matter.
These soils tend to lose moisture more quickly and to a greater degree than soils that contain higher amounts of clay. Conversely, in those soils that contain relatively higher amounts of clay, the deactivation of the sulfoxide herbicide is less troublesome.
The term "dry soil" as used herein means soil that contains less than about 10 percent moisture. When the moisture level in the soil is less than about 10 percent, deactivation of the sulfoxide herbicide has been observed. Moisture levels of less than 6-7 percent cause severe deactivation of the sulfoxide herbicide.